rent arrears and end of tenancy

Possession - Section 8 and Section 21

hi , my tenant has rent arrears and the lease expires March 6 2014. If possible I would like to try and obtain the rent arrears and ask him to leave on the due date. The deposit is protected and I followed all the rules when collecting this.

I am not sure he has any money as the rent is being paid by the local authority , I just wondered how (1) best to make sure he leaves ,(2) get the arrears or at least the months deposit (3) general advice on what to do next would a section 21 or section 8 be best or both

any suggestion would be welcome

thanks